Fast-growing Facebook has purchased two pieces of property near the former Sun Microsystems campus in Menlo Park, acquisitions that could bolster the footprint of the expected future headquarters of the social network.

Records filed with the San Mateo County recorder’s office show that Giant Properties LLC, an entity connected to Facebook, bought the properties at 312 and 314 Constitution Drive on Dec. 27 from Argonaut Holdings. Giant paid a transfer tax of $22,577, suggesting a purchase price of about $20.5 million for the two properties.

Multiple sources familiar with Facebook’s plans say the company could close as soon as next month on the 57-acre former Sun campus off Willow Road, which housed about 3,000 Sun employees last year, before Oracle bought the struggling computer maker for $7.4 billion. The former Sun campus is a short distance from and linked to the Constitution Drive properties by a pedestrian walkway, and Facebook is thought to be interested in the new properties for employee parking.

Facebook now has more than 2,000 employees, many of them shoehorned into 150,000 square feet the company leases in Stanford Research Park in Palo Alto. Pat Burt, whose term as mayor of Palo Alto ended several weeks ago, said the city has had extensive talks with Facebook in recent months about how it might stay in Palo Alto, but the social network company’s growth plans are so ambitious that sufficient space wasn’t available.

“If they could have a million square feet adjacent to where they are, that’s their first choice,” Burt said in a recent interview. “It’s just not possible.”

Facebook did not respond to e-mails seeking comment Thursday.

Although county real estate records do not name Facebook as the buyer, they list the buyer’s address as 1050 Page Mill Road in Palo Alto, a building occupied by Facebook. John Tenanes, Facebook’s real estate chief, handled the transaction for the buyer, county real estate records show.

Before settling on the former Sun campus, Facebook had also been considering the 98-acre former Hewlett-Packard campus in Cupertino, until Apple bought that property in November.

Bay Area News Group reporters Pete Carey and George Avalos contributed to this report. Contact Mike Swift at 408-271-3648. Follow him at Twitter.com/swiftstories.

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